Solubility behaviors of CFC-113 (CFCl2-CF2Cl), CFC-113a (CCl3-CF3), CFC-114 (CF2Cl-CF2Cl), CFC-114a (CFCl2-CF3), HCFC-123 (CHCl2-CF3), HCFC-123a (CHClF-CF2Cl), HCFC-124 (CHFCl-CF3), HCFC-124a (CHF2-CF2Cl), HFC-134 (CHF2-CHF2), and HFC-134a (CH2F-CF3) in room-temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([emim][Tf2N]) have been investigated using a gravimetric microbalance method from (283 to 348) K or volumetric and cloud-point methods. In the case of the perhalogenated compounds (CFC-113, CFC-114, and their isomers), the solubility behavior between isomers in the ionic liquid is practically identical with large immiscibility gaps. This suggests that the (present) ionic liquid cannot be used for these isomer separations. However, the monohydrogen substituted halocarbons (HCFC-123, HCFC-124, and their isomers) begin to show some difference (liquid-liquid immiscibility gap) in the ionic liquid. The isomer effect on the solubility in the ionic liquid becomes significant for the dihydrogen-substituted halocarbons (HFC-134 and HFC-134a), and these isomers can be separated using [emim][Tf2N] as an entrainer in an extractive distillation. This observation is consistent with our earlier findings for various HFCs in ionic liquids.